The purest penetration testers will often comment that using an automated vulnerability scanner is cheating, but in some cases, such as penetration testing, with a limited amount of time, vulnerability scanners are critical to gaining a great deal of information about a target network, in a short amount of time. In Chapter 1, Beginning with Kali Linux, we discussed how to install additional tools into Kali Linux. One such tool was the vulnerability scanner, Nessus. In regards to vulnerability assessment tools, Nessus is a great addition to your tool set.
As previously stated, we have addressed installing Nessus in a previous section, so in this chapter we will focus on configuring and executing a vulnerability scan against two targets; a Windows XP workstation and the vulnerable Metasploitable Linux Distribution. From those, you can gain a good understanding of how to use the tool.
To configure a vulnerability scan:
https://localhost:8834 and log in. Once you log into Nessus, you will be brought to the Scans page:


Complete the Name, Description and Targets boxes. These are all that are necessary to complete a scan but, as you can see, in the left-hand column, there are a number of different settings. Each of these allows you to customize the scan to fit your specific requirements:




This information includes not only information about the vulnerability, but also information on whether there is an exploit available. This allows the penetration tester the ability to craft additional attacks against these vulnerabilities.
Nessus is a powerful tool to use in any penetration testing engagement. It provides a great deal of information and functionality that could not be addressed in this section. It is recommended that you spend some time understanding the features available and how to use them. In addition, Tenable makes the home version free for you to test with. In the event that you have external IPs, or are using Nessus for a client, you will have to use the paid version.